Congenital peritoneopericardial diaphragmatic hernia was diagnosed in a four-year-old miniature Schnauzer with a one-year history of sporadic episodes of an anxious, painful attitude, licking at the anal area, dyschezia and excessive maintenance of a sitting posture. Intermittent diarrhea, vomiting and panting were also noted. Survey radiographs of the thorax revealed a greatly enlarged cardiac silhouette and an obscured diaphragmatic border. Surgical correction was successful and recovery was uncomplicated. Fourteen additional case histories in nine dogs and five cats diagnosed with congenital peritoneopericardial diaphragmatic hernias at the New York State College of Veterinary Medicine over the past fifteen years were reviewed. A summary of the history, clinical and radiographic presentations, and surgical findings is presented.